One aspect of Amgen’s sustainability initiative focuses on medicinal chemistry. “Although the scale of reaction is small, the cumulative footprint is significant,” noted Emily Peterson, Ph.D., scientist and green chemistry team lead for Amgen Massachusetts (AMA) medicinal chemistry.
The goal at Amgen, then, is to “equip medicinal chemists with working knowledge of green chemistry, provide access to tools to guide green solvent and reagent selection, and apply restraint rather than constraint,” to chemists’ choices. Immediate challenges include reducing chlorinated solvent usage, phasing out toxic and noneconomical reagents, modifying wasteful ordering and disposal habits, and encouraging use of green conditions.
These changes are seeing results. For example, since November 2010, the use of dichloromethane at the AMA site has declined 40%. “Ten percent was achieved just by picking up a different squirt bottle when chemists rinsed their tubes,” Dr. Peterson explained.
Much of the rest was achieved by education and replacing dichloromethane chromatography with greener solvent systems (like heptanes, ethyl acetate, and ethanol) and by replacing normal-phase chromatography with reverse-phase medium-pressure liquid chromatography, which allows purification of highly polar compounds using aqueous media.
“You can load large amounts onto the column, including crude reaction mixtures, and you can reuse the columns, which gives nice flexibility,” Dr. Peterson added.
At Amgen, “we also crafted our own green chemistry solvent selection guide. We made it into magnets and put them on all the hoods, so chemists are reminded daily of greener options.”
At Dr. Peterson’s site, the T3P amide coupling reagent has become a popular reagent in medicinal chemistry, she said. “You can work it up with water, and the product is often pure enough to go to the next step without contamination with other reagents.”
To reduce waste, Amgen partners with ASDI to store its chemicals. Therefore, research sites can order just the quantities they need from among Amgen’s own supplies. The company also changed its chemical disposal policy, retaining chemicals with long-term stability rather than discarding all chemicals after three years. In shipping 500 compounds to ASDI, “we saved $3,000 on disposal alone.”
Chemists contemplating green chemistry cite concerns about re-optimization timeframes, costs, access to established chemicals, or methods and regulatory issues. “The key to adoption is to use green technologies that are superior to current methods.” Amgen also operates a green chemistry awards program for labs that make the greatest green chemistry gains. “Cash talks,” she said.